Since polycarbonate resin is superior in transparency, mechanical properties, electric properties, heat resistance, dimensional stability, and the like as a general-purpose engineering plastic, it has been used in wide ranged fields such as parts of electric/electronic equipment components, office automation equipments, machine components, car parts, construction members, various kinds of containers, leisure goods and groceries.
Among these application fields, in information display devices for computers, televisions, and the like, including thin film transistors (TFT), a display device incorporated with reflection plate in which a high degree of light beam reflectance is required, such as reflection plate for backlight of liquid crystal display devices and reflection plate for illuminated type pushbutton switches and photoelectric switches is becoming popularly used.
For these light reflective members in which a high degree of light beam reflectance is required, molded resin articles or the like obtained by molding a polycarbonate resin composition having a high content of particulate such as titanium oxide from the viewpoints of light reflectivity, formability and impact strength have been used.
For the light reflection members consisting of polycarbonate resin composition, flame retardation has been strongly required, and in order to respond this request, a number of technologies in which flame retardation is achieved by blending halogen-based compound, phosphorus-based compound, siloxane-based compound, polytetrafluoroethylene, and the like into an aromatic polycarbonate resin have been proposed. Recently, out of consideration for environment, instead of using bromine-based flame retardant or phosphorus-based flame retardant, a flame retardant resin composition using other type of flame retardant is demanded.
As a flame retardant polycarbonate in which an organometallic salt is blended, for example, Patent Literature 1 describes a resin composition comprising polycarbonate resin, sodium salt of aromatic sulfonic acid and polytetrafluoroethylene. However, the resin composition of Patent Literature 1 is inferior in reflecting property and flame retardancy in thin-walled product due to no addition of titanium oxide, therefore the resin composition cannot be said to have sufficient performance as a flame retardant light reflective material.
Also, Patent Literature 2 describes a resin composition in which a metal salt of aromatic sulfonic acid showing pH 6.4 to 7.5 (specifically, sodium salt of branched dodecylbenzenesulfonic acid) (B) and polytetrafluoroethylene are blended in polycarbonate resin (A). However, the resin composition of Patent Literature 2 is also insufficient for thin-walled products use, because combustibility for a thickness less than 1.5 mm does not satisfy the level of V-0, due to no addition of titanium oxide.
In addition, as an example of flame retardant polycarbonate in which non-phosphorus-based flame retardant and titanium oxide are used in combination, for example, Patent Literature 3 describes a resin composition comprising a polycarbonate resin, a silicone-based flame retardant in which polyorganosiloxane polymer is supported on silica, and polytetrafluoroethylene, which exhibits UL flame retardancy of V-0 for 1.5 mm. However, the resin composition of Patent Literature 3 tends to have poor appearance such as flow mark occurring during molding by inorganic silica in the flame retardant, and silver streak by elimination of low viscosity polydimethylsiloxane, therefore cannot be said to have sufficient performance as a member in which designing property is particularly demanded.
On the other hand, examples of flame retardant polycarbonate resin composition in which an organometallic salt and titanium oxide are used in combination include Patent Literatures 4 to 6.
Patent Literature 4 describes a resin composition in which titanium oxide (B) and 1 to 8 parts by weight (parts by mass) of alkylbenzenesulfonate type antistatic agent (C) are added to polycarbonate resin (A). However, in the resin composition of this Patent Literature 4, molecular weight of polycarbonate tends to decrease significantly during molding due to too large amount of alkali metal salt to be added, and formability and flame retardancy tend to be deteriorated.
Also, Patent Literature 5 describes a resin composition in which polytetrafluoroethylene (B), organometallic salt (E), silicone compound (D), and further specified titanium oxide are added to polycarbonate resin (A). However, in the resin composition of Patent Literature 4, since poor appearance such as silver streak greatly depends on rather secondary aggregation state of titanium oxide, a satisfactory result can be hardly obtained with the titanium oxide described in the claims of the Literature. In addition, poor appearance tends to occur by addition of a silicone compound.
Further, Patent Literature 6 describes a flame retardant resin composition in which polytetrafluoroethylene, organometallic salt, silicone compound and titanium oxide are added to polycarbonate resin. However, these compositions are inferior in high temperature stability and residence stability, and impact resistance and appearance tend to deteriorate remarkably.
As for surface treatment with titanium oxide, for example, Patent Literature 7 describes that needle-like titanium oxide treated with polyorganosiloxane is used in polycarbonate resin. However, only by surface-treating titanium oxide with polyorganosiloxane, poor appearance such as silver streak tends to easily occur.